The present invention relates generally to a field of image storage and archiving systems using image compression and decompression, and more particularly to a technique for creation and management of compressed image files by rapidly compressing and decompressing image data by optimal compression ratios to create hybrid compressed data files which may be stored and exchanged in a client-server system architecture.
Picture archiving and communication; systems, or PACS, have become an extremely important component in the management of digitized image data, particularly in the field of medical imaging. Such systems often function as central repositories of image data, receiving the data from various sources, such as medical imaging systems. The image data is stored and made available to radiologists, diagnosing and referring physicians, and other specialists via network links. Improvements in PACS have led to dramatic advances in the volumes of image data available, and have facilitated loading and transferring of voluminous data files both within institutions and between the central storage location or locations and remote clients.
A major challenge to further improvements of PACS in medical diagnostic applications is the handling of the large, data files created in examinations. Depending upon the modality, digitized data may be acquired and processed for a substantial number of images in a single examination, each image representing a large data set defining discrete picture elements or pixels of a reconstructed image. Computed Tomography (CT) imaging systems, for example, can produce numerous separate images along an anatomy of interest in a very short examination timeframe. Ideally, all such images are stored centrally on the PACS, and made available to the radiologist for review and diagnosis.
Various techniques have been proposed and are currently in use for analyzing and compressing large data files, such as medical image data files. Image data files typically include streams of data descriptive of image characteristics, typically of intensities or other characteristics of individual pixels in the reconstructed image. In the medical diagnostic field, these image files are typically created during an image acquisition or encoding sequence, such as in an x-ray system, a magnetic resonance imaging system, a computed tomography imaging system, and so forth. The image data is then processed, such as to adjust dynamic ranges, or to enhance certain features shown in the image, for storage, transmittal and display.
While image files may be stored in raw and processed formnats, many image files are quite large, and would occupy considerable memory space. The increasing complexity of imaging systems also has led to the creation of very large image files, typically including more data as a result of the useful dynamic range of the imaging system, the size of the matrix of image pixels, and the number of images acquired per examination.
In addition to occupying large segments of available memory, large image files can be difficult or time consuming to transmit from one location to another. In a typical medical imaging application, for example, a scanner or other imaging device will typically create raw data which may be at least partially processed at the scanner. The data is then transmitted to other image processing circuitry, typically including a programmed computer, where the image data is further processed and enhanced. Ultimately, the image data is stored either locally at the system, or in the PACS for later retrieval and analysis. In all of these data transmission steps, the large image data file must be accessed and transmitted from one device to another.
Current image handling techniques include compression of image data within the PACS environment to reduce the storage requirements and transmission times. Such compression techniques may, however, compress entire files, including descriptive header information which could be useful in accessing or correlating images for review. Moreover, current techniques do not offer sufficiently rapid compression and decompression of image files to satisfy increasing demands on system throughput rates and access times. Finally, alternative compression and decompression techniques do not offer the desired compression ratios, in combination with rapid compression and decompression in a client-server environment.
There is a need, therefore, for an improved PACS technique which provides rapid compression and decompression of image files, and which obtains improved compression ratios. There is a particular need for a PACS capable of creating hybrid compressed files, optimally compressing image data in accordance with one or more compression algorithms, while maintaining descriptive data uncompressed for reference. There is also a need for a PACS that provides these benefits in a clientserver environment, enabling the hybrid compressed files to be freely exchanged and accessed between one or more servers and internal or external clients, while permitting compression algorithms to be updated and improved with minimal perturbation to the client systems.
The invention provides an improved picture archiving and communication system designed to respond to these needs. The system makes use of extremely fast compression and decompression techniques to create hybrid compressed image data files. The hybrid files include header portions containing descriptive data which may be used both for the compression and decompression processes, as well as for access, retrieval and management of the data once compressed. A server receives the hybrid files and makes the files available for decompression and viewing at client stations. The header portion of the files may include DICOM compliant data, further facilitating the access of images by radiologists and other specialists in medical diagnostic applications. The use of the hybrid files greatly facilitates workflow by enabling the files to be identified, ordered, transmitted, and so forth. The hybrid files also substantially reduce the time required for transmission of image data within the system, while making the files readily accessible by virtue of the server-client environment.